1. Field
The present invention relates generally to telecommunications, and, more specifically, the invention relates to cellular communication systems.
2. Background
A modern communication system is expected to provide reliable data transmission for a variety of applications, such as voice and data applications. In a point-to-multipoint communications context, known communication systems are based on frequency division multiple access (FDMA), time division multiple access (TDMA), code division multiple access (CDMA), and perhaps other multiple access communication schemes.
A CDMA system may be designed to support one or more CDMA standards, such as (1) the “TIA/EIA-95 Mobile Station-Base Station Compatibility Standard for Dual-Mode Wideband Spread Spectrum Cellular System” (this standard with its enhanced revisions A and B may be referred to as the “IS-95 standard”), (2) the “TIA/EIA-98-C Recommended Minimum Standard for Dual-Mode Wideband Spread Spectrum Cellular Mobile Station” (the “IS-98 standard”), (3) the standard sponsored by a consortium named “3rd Generation Partnership Project” (3GPP) and embodied in a set of documents known as the “W-CDMA standard,” (4) the standard sponsored by a consortium named “3rd Generation Partnership Project 2” (3GPP2) and embodied in a set of documents including “TR-45.5 Physical Layer Standard for cdma2000 Spread Spectrum Systems,” the “C.S0005-A Upper Layer (Layer 3) Signaling Standard for cdma2000 Spread Spectrum Systems,” and the “TIA/EIA/IS-856 cdma2000 High Rate Packet Data Air Interface Specification” (the “cdma2000 standard” collectively), (5) the 1xEV-DO standard, and (6) certain other standards. The standards expressly listed above are incorporated by reference as if fully set forth herein, including annexes, appendices, and other attachments.
Data-optimized or “DO” cellular communication systems have been developed to satisfy the constantly increasing demand for wireless data services. As the name implies, DO systems are optimized for data transmission (as opposed to voice transmission), and in particular such systems are optimized for downlink data transmission. Data-optimized systems need not exclude uplink data transmission, or voice transmission in either direction. It should be noted that voice may also be transmitted as data, for example, in the case of voice over internet protocol (VoIP) transmissions.
In cellular DO CDMA systems, reverse link data may be transmitted over the air interface using any one of a number of predefined packet sizes, for example, 128, 256, 512, 768, 1024, 1536, 2048, 3072, 4096, 6144, 8192, 12288 bit sizes. Generally, the sizes correspond to different rates, although the use of incremental redundancy with Hybrid Automatic Repeat-reQuest (HARQ) may affect the actual rates achieved in the field.
Some applications provide packets that do not fall neatly into one of the predefined sizes. For example, a vocoder (voice encoder) of a VoIP telephony application may provide periodic packets of 300 bits. According to one approach, such situations may be handled by choosing a smallest predefined packet size that is still larger than the packet size provided by the application. For a 300-bit application packet size, a 512-bit packet size may thus be selected on the reverse link of the air interface. The larger size packet is then used to transmit at least a portion of two or more packets provided by the vocoder (or another application). This approach leads to additional delay, because of the necessity to wait to assemble multiple vocoder packets into a single air interface packet. The additional delay may be excessive for the quality of service (QoS) of the application. To avoid the additional delay, another approach fits one user application packet into the larger size air interface packet, and stuffs the leftover bits in the larger size packet. This approach wastes the stuffed bits and thus causes a loss of spectral efficiency, increased interference, and decreased battery life.
Therefore, there is a need in the art for methods and apparatus that would improve packing efficiency and spectral efficiency on the reverse link. There is also a need in the art for methods and apparatus that would improve reverse link efficiencies for delay-sensitive applications. There is a further need in the art for methods and apparatus that would improve reverse link efficiencies for delay-sensitive applications while at the same time maintaining backward compatibility with legacy access terminals, and minimizing or eliminating hardware changes to the radio network.